UV-Assisted Stripping of Hardened Photoresist to Create Chemical Templates for Directed Self-Assembly

ABSTRACT

A processing method is disclosed that enables an improved directed self-assembly (DSA) processing scheme by allowing the formation of improved guide strips in the DSA template that may enable the formation of sub-30 nm features on a substrate. The improved guide strips may be formed by improving the selectivity of wet chemical processing between different organic layers or films. In one embodiment, treating the organic layers with one or more wavelengths of ultraviolet light may improve selectivity. The first wavelength of UV light may be less than 200 nm and the second wavelength of UV light may be greater than 200 nm.

CROSS REFERENCE TO RELATED APPLICATION

Pursuant to 37 C.F.R. §1.78(a)(4), this application claims the benefitof and priority to prior filed co-pending Provisional Application Ser.No. 61/873,515 filed Sep. 4, 2013.

FIELD OF THE INVENTION

This invention relates to semiconductor processing technology, and moreparticularly, to methods for directed self-assembly of block copolymers(BCP) on a substrate.

BACKGROUND OF THE INVENTION

Photolithography is a semiconductor manufacturing technique that may beused to generate patterns on the substrate that may be used to form theintegrated circuits or electronics devices. Cost and performanceimprovements in semiconductor devices may be accomplished by increasingdevice density on a substrate. One approach to achieve higher devicedensity may be to increase miniaturization of features being formed on asemiconductor substrate. Accordingly, new methods or techniques togenerate smaller patterns would be desirable.

Self-assembly of block copolymers (BCP) have been used as a tool fordecreasing patterned feature sizes using standard photolithographytechniques. BCPs may be useful in semiconductor manufacturing becausethey may form ordered, chemically distinct templates with dimensions ofless than 30 nm. The geometry of the template may be manipulated by themolecular weight and composition of the different block types of thecopolymer. The template may comprise two or more areas of differingchemical activity that periodically alternate. In one approach, one ofthe areas of chemical activity may be attractive to one of the blockcopolymer phases, while the other area of chemical activity may beneutral to both blocks of the BCP. In one instance, the attractive areamay force the BCP to align above it, and then the alternate BCP may beforced to align next to this pinned phase. In this way, the blockcopolymer can be directed to self-assemble in parallel to the pinningguides over large areas of the substrate.

The template may be formed using different organic materials that may bepatterned with organic photoresist. In this instance, the patterningprocess may need to include a removal process or method that increasesthe selectivity between the exposed and unexposed organic materials onthe substrate.

SUMMARY

This disclosure relates to a directed self-assembly templatemanufacturing process that incorporates the deposition, patterning, andremoval of organic materials to form a patterning template for sub-30 nmstructures. More particularly, in one specific embodiment, the templatemay be formed by patterning and etching a polystyrene layer deposited ona substrate. An organic photoresist may be deposited on the polystyrenelayer and the patterning/etch process may result in a residual organicpolymer being formed on a sidewall of the polystyrene layer that may notbe covered by the photoresist. Ideally, the removal of the photoresistand the residual polymer may be done using the same process orchemistry.

In one embodiment, the template may be formed by depositing a polymer(e.g., polystyrene) on a substrate used to manufacture semiconductordevices. The polymer may be heated to a bake temperature (e.g., <310 C)for a period of time that may increase the density of the polymer andmay cross-link the polymer. A photoresist layer may be deposited on thepolymer and patterned to expose the underlying polymer. A portion of thepolymer that is not covered by the photoresist may be removed using adry or wet etch process. In certain instances, the etch process maydeposit a residual polymer on a sidewall of the polymer not covered bythe photoresist and the photoresist. However, the presence of theresidual polymer may not be desired with the formation of the template.Accordingly, the removal of the photoresist and the residual polymerusing the least amount of process steps may be desirable. For example,oxygen and ultra-violet (UV) light may be used to oxidize a portion ofthe photoresist and/or change the surface state of the residual polymer,such that the photoresist and residual polymer may be removed withminimal impact to the geometry and/or surface properties of theunderlying polymer. The UV light may include a first wavelength and asecond wavelength, such that the first wavelength is greater than 200 nmand the second wavelength is less than 200 nm. The UV light may have adose between 0.01 J/cm2 to 150 J/cm2. In another embodiment, at least10% of the UV light exposed to the substrate may have a wavelength lessthan 200 nm. In one specific embodiment, the first wavelength being 185nm and the second wavelength being 254 nm.

Following the UV light exposure, a wet chemical etch may be done using avariety of chemistries, which may include, but is not limited to acombination of deionized water, ammonium hydroxide, and hydrogenperoxide or tetramethylammonium hydroxide and dimethyl sulfoxide or acombination thereof. The clean chemistry may need to demonstrateselectivity between the polymer, residual polymer, and the photoresist.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate embodiments of the invention and,together with a general description of the invention given above, andthe detailed description given below, serve to explain the invention.Additionally, the left most digit(s) of a reference number identifiesthe drawing in which the reference number first appears.

FIGS. 1A-1C include an illustration of a flow diagram with correspondingillustrations for a method to generate at least a portion of a directedself-assembly template used to manufacture a semiconductor device on asubstrate.

FIG. 2 includes cross-section illustrations of aligned block copolymersthat may be formed using, but is not limited to, the method described inthe description of FIGS. 1A-1C.

FIG. 3 includes an illustration of a flow diagram with correspondingillustrations for a method to remove a first organic layer disposedabove a second organic layer formed on a substrate.

DETAILED DESCRIPTION

The following Detailed Description refers to accompanying drawings toillustrate exemplary embodiments consistent with the present disclosure.References in the Detailed Description to “one embodiment,” “anembodiment,” “an exemplary embodiment,” etc., indicate that theexemplary embodiment described can include a particular feature,structure, or characteristic, but every exemplary embodiment does notnecessarily include the particular feature, structure, orcharacteristic. Moreover, such phrases are not necessarily referring tothe same embodiment. Further, when a particular feature, structure, orcharacteristic is described in connection with an embodiment, it iswithin the knowledge of those skilled in the relevant art(s) to affectsuch feature, structure, or characteristic in connection with otherexemplary embodiments whether or not explicitly described.

The exemplary embodiments described herein are provided for illustrativepurposes, and are not limiting. Other embodiments are possible, andmodifications can be made to exemplary embodiments within the scope ofthe present disclosure. Therefore, the Detailed Description is not meantto limit the present disclosure. Rather, the scope of the presentdisclosure is defined only in accordance with the following claims andtheir equivalents.

The following Detailed Description of the exemplary embodiments will sofully reveal the general nature of the present disclosure that otherscan, by applying knowledge of those skilled in the relevant art(s),readily modify and/or adapt for various applications such exemplaryembodiments, without undue experimentation, without departing from thescope of the present disclosure. Therefore, such adaptations andmodifications are intended to be within the meaning and plurality ofequivalents of the exemplary embodiments based upon the teaching andguidance presented herein. It is to be understood that the phraseologyor terminology herein is for the purpose of description and notlimitation, such that the terminology or phraseology of the presentspecification is to be interpreted by those skilled in relevant art(s)in light of the teachings herein.

As used herein, the term “radiation sensitive material” means andincludes photosensitive materials such as photoresists.

As used herein, the term “polymer block” means and includes a groupingof multiple monomer units of a single type (i.e. a homopolymer block) ormultiple types (i.e., a copolymer block) of constitutional units into acontinuous polymer chain of some length that forms part of a largerpolymer of an even greater length and exhibits a χN value, with otherpolymer blocks of unlike monomer types, that is sufficient for phaseseparation to occur. χ is the Flory-Huggins interaction parameter and Nis the total degree of polymerization for the block copolymer. Accordingto embodiments of the present invention, the χN value of one polymerblock with at least one other polymer block in the larger copolymer maybe equal to or greater than about 10.5.

As used herein, the term “block copolymer” means and includes a polymercomposed of chains where each chain contains two or more polymer blocksas defined above and at least two of the blocks are of sufficientsegregation strength (e.g., χN>10.5) for those blocks to phase separate.A wide variety of block polymers are contemplated herein includingdi-block copolymers (i.e., polymers including two polymer blocks (AB)),tri-block copolymers (i.e., polymers including three polymer blocks (ABAor ABC)), multi-block copolymers (i.e., polymers including more thanthree polymer blocks (ABCD, etc.)), and combinations thereof.

As used herein, the term “substrate” means and includes a base materialor construction upon which materials are formed. It will be appreciatedthat the substrate may include a single material, a plurality of layersof different materials, a layer or layers having regions of differentmaterials or different structures in them, etc. These materials mayinclude semiconductors, insulators, conductors, or combinations thereof.For example, the substrate may be a semiconductor substrate, a basesemiconductor layer on a supporting structure, a metal electrode or asemiconductor substrate having one or more layers, structures or regionsformed thereon. The substrate may be a conventional silicon substrate orother bulk substrate comprising a layer of semiconductor material. Asused herein, the term “bulk substrate” means and includes not onlysilicon wafers, but also silicon-on-insulator (“SOI”) substrates, suchas silicon-on-sapphire (“SOS”) substrates and silicon-on-glass (“SOG”)substrates, epitaxial layers of silicon on a base semiconductorfoundation, and other semiconductor or optoelectronic materials, such assilicon-germanium, germanium, gallium arsenide, gallium nitride, andindium phosphide. The substrate may be doped or undoped.

The terms “microphase segregation” and “microphase separation,” as usedherein mean and include the properties by which homogeneous blocks of ablock copolymer aggregate mutually, and heterogeneous blocks separateinto distinct domains. In the bulk, block copolymers can self-assembleinto ordered morphologies, having spherical, cylindrical, lamellar,bicontinuous gyroid, or miktoarm star microdomains, where the molecularweight of the block copolymer dictates the sizes of the microdomainsformed.

The domain size or pitch period (L₀) of the self-assembled blockcopolymer morphology may be used as a basis for designing criticaldimensions of the patterned structure. Similarly, the structure period(L_(S)), which is the dimension of the feature remaining afterselectively etching away one of the polymer blocks of the blockcopolymer, may be used as a basis for designing critical dimensions ofthe patterned structure. The lengths of each of the polymer blocksmaking up the block copolymer may be an intrinsic limit to the sizes ofdomains formed by the polymer blocks of those block copolymers. Forexample, each of the polymer blocks may be chosen with a length thatfacilitates self-assembly into a desired pattern of domains, and shorterand/or longer copolymers may not self-assemble as desired.

The term “baking” or “bake” as used herein means and includes treatmentof the block copolymer so as to enable sufficient microphase segregationbetween the two or more different polymeric block components of theblock copolymer to form an ordered pattern defined by repeatingstructural units formed from the polymer blocks. Baking of the blockcopolymer in the present invention may be achieved by various methodsknown in the art, including, but not limited to: thermal annealing(either in a vacuum or in an inert atmosphere, such as nitrogen orargon), solvent vapor-assisted annealing (either at or above roomtemperature), supercritical fluid-assisted annealing, orabsorption-based annealing (e.g., optical baking). As a specificexample, thermal annealing of the block copolymer may be conducted byexposing the block copolymer to an elevated temperature that is abovethe glass transition temperature (T_(g)), but below the degradationtemperature (T_(d)) of the block copolymer, as described in greaterdetail hereinafter. Other conventional annealing methods not describedherein may also be utilized.

The ability of block copolymers to self-organize may be used to formmask patterns. Block copolymers are formed of two or more chemicallydistinct blocks. For example, each block may be formed of a differentmonomer. The blocks are immiscible or thermodynamically incompatible,e.g., one block may be polar and the other may be non-polar. Due tothermodynamic effects, the copolymers will self-organize in solution tominimize the energy of the system as a whole; typically, this causes thecopolymers to move relative to one another, e.g., so that like blocksaggregate together, thereby forming alternating regions containing eachblock type or species. For example, if the copolymers are formed ofpolar (e.g., organometallic-containing polymers) and non-polar blocks(e.g., hydrocarbon polymers), the blocks will segregate so thatnon-polar blocks aggregate with other non-polar blocks and polar blocksaggregate with other polar blocks. It will be appreciated that the blockcopolymers may be described as a self-assembling material since theblocks can move to form a pattern without active application of anexternal force to direct the movement of particular individualmolecules, although heat may be applied to increase the rate of movementof the population of molecules as a whole.

In addition to interactions between the polymer block species, theself-assembly of block copolymers can be influenced by topographicalfeatures, such as steps or guides extending perpendicularly from thehorizontal surface on which the block copolymers are deposited. Forexample, a di-block copolymer, a copolymer formed of two differentpolymer block species, may form alternating domains, or regions, whichare each formed of a substantially different polymer block species. Whenself-assembly of polymer block species occurs in the area between theperpendicular walls of a step or guides, the steps or guides mayinteract with the polymer blocks such that—e.g., each of the alternatingregions formed by the blocks is made to form a regularly spaced apartpattern with features oriented generally parallel to the walls and thehorizontal surface.

Such self-assembly can be useful in forming masks for patterningfeatures during semiconductor fabrication processes. For example, one ofthe alternating domains may be removed, thereby leaving the materialforming the other region to function as a mask. The mask may be used topattern features such as electrical devices in an underlyingsemiconductor substrate. Methods for forming a block copolymer mask aredisclosed in U.S. application Ser. No. 13/830,859, CHEMI-EPITAXY INDIRECTED SELF-ASSEMBLY APPLICATIONS USING PHOTO-DECOMPOSABLE AGENTS, bySomervell, et al., filed on Mar. 14, 2013.

FIGS. 1A-1B include a flow diagram 100 for a method to generate adirected self-assembly (DSA) template to be used to etch sub-30 nmfeatures into a substrate 104 and corresponding cross-sectionillustrations 102 to illustrate the method 100. The DSA template may beused to achieve uniform and small scale patterns (e.g., <30 nm) on thesubstrate 104. In one embodiment, the self-assembly of BCPs based on thesurface properties of DSA template may include two or more areas withdifferent surface properties that may alternate throughout the DSAtemplate. One approach to forming the DSA template may include forming aguide material on the substrate 104 that may include lines narrow lineswith a width of less than 20 nm that form a pattern on the substrate104. The guide material (e.g., organic polymer 126) may be formed bypatterning with an organic photoresist deposited on the unpatternedguide material. The patterning of the guide material may include theremoval of a portion of the guide material using an etch process thatmay deposit a residual polymer on a sidewall of the guide material.Ideally, the organic photoresist can be removed from the organic guidematerial without impacting the geometry or surface properties that wouldnegatively impact subsequent processing. Accordingly, a selectiveremoval scheme that enables the selective removal of the organicphotoresist and the residual polymer, but maintaining the surfaceproperties and geometry of the polymer may be desirable. For example,the geometry or profile of the polymer may form a substantially squareor rectangular shape with uniform surfaces and the bonds at the surfaceare strong enough to maintain that profile during subsequent processingof the substrate 104.

Although the method 100 will be described as multiple discrete optionsfor the purposes of explanation. However, the order of descriptionshould not be construed as to imply that these operations arenecessarily order dependent. In particular, these operations may notneed to be performed in the order of presentation. The method 100 may beperformed in a different order that the described embodiment. Further,some of the operations may also be omitted or may have additionaloperations performed in order to form the DSA template.

At block 106, an organic polymer 126 may be deposited on the substrate104 to form the foundation for the DSA template. The organic polymer 126may include, but is not limited to, polystyrene that may be cross linkedwhen baked at above room temperature. The cross linking may increase thestrength of the organic polymer 126 to resist structural changes causedby subsequent processing of the substrate 104. For example, the crosslinked organic polymer 126 may be less likely to be removed or deformedby subsequent layer deposition, patterning, and/or cleaning of thesubstrate 104. In one embodiment, the baking of the organic polymer 126may increase density of the organic polymer 126 by using a baketemperature between 200 C and 310 C.

The deposited organic polymer 126 may be deposited in a relativelyuniform thickness that may be continuous across a surface of thesubstrate 104. However, the DSA template may be implemented usingdiscrete portions of the organic polymer 126 to enable sub-30 nmfeatures on the substrate 104. Accordingly, the organic polymer 126 maybe patterned using photolithography techniques.

At block 108, a photoresist layer 128 may be deposited on the organiclayer 126 in a uniform and/or conformal manner. The photoresist layer128 may be any radiation sensitive composition that chemically reactswhen exposed to visible light, deep ultraviolet (DUV) light, extremeultraviolet (EUV) light, electron beam and X-ray radiant energy areradiation types commonly used today in photolithography processes. Whenexposed to radiation, the bonds of the molecules in the photoresistlayer 128 may break or become more soluble, such that the exposedportion may be dissolved using a photoresist developer chemical. Thephotoresist layer 128 may be a positive tone photoresist. A positivetone photoresist may become more soluble when exposed to radiation and anegative tone photoresist may become less soluble when exposed toradiation. In one embodiment, the positive tone photoresist or thenegative tone photoresist may include, but is not limited to, one ormore of the following: protected or unprotected copolymers ofmethacrylic, protected or unprotected acrylic conmonomers, styrene,hyrdoxystyrene, or protected or unprotected hyrdoxystyrene comonomers.The exposure of radiation may be controlled by a patterning process thatmay expose discrete portions of the photoresist layer 128 to radiationusing known photolithography equipment and techniques. In anotherembodiment, the photoresist layer 128 may a negative tone photoresistthat may become less soluble in a different type of developer than thepositive tone photoresist, such that the exposed portion of the negativetone photoresist layer remains intact, while the unexposed portion maybe removed.

At block 110, the photoresist layer 128 may be patterned by exposingdiscrete portions of radiation (e.g., light) to make those exposedregions, in one embodiment, more soluble or more easily removed toexpose portions of the organic polymer layer 126. The exposed portions130 of the organic polymer 126 may be exposed to subsequent processinglike etching or cleaning. The DSA template pattern may include straightlines that form a substantially square or rectangular cross sectionprofile of the photoresist layer 128, as shown in FIG. 1A. The exposedportions 130 of the organic polymer 126 are opposite from the portionsof the photoresist layer 128 that may be have been removed during achemical and/or plasma processing that are not shown the flow diagramfor method 100 in FIGS. 1A-1B.

At block 112, a chemical process may be used to remove or etch theexposed portions 130 of the organic polymer 126 in a manner thattransfers the pattern of the photoresist layer 128 to the organicpolymer 126. The chemical process may include, but is not limited to, agas that generates a residual polymer 132 on at least one sidewall ofthe organic polymer 126 and the photoresist layer 128 during the removalprocess. For example, as the organic polymer 126 is removed using thegas (e.g., CF4), a passivating polymer (e.g., residual polymer 132) maybe formed as a by-product of the removal process. Unfortunately, theresidual polymer 132 may interfere with the implementation of the DSAtemplate to form sub-30 nm features in the substrate 104. For example,the organic polymer 126 and the photoresist layer 128 may be trimmed(not shown) to a thinner width to create a DSA template that can enablesmaller features than the patterns provided in previous patterningprocess (e.g., block 110). The trimming may include additionalpatterning and etching of both layers that narrows the width of theorganic polymer 126. The residual polymer 132 may interfere with thetrimming process. Accordingly, the residual polymer 132 may be removedto improve the performance or capability of the DSA techniques. Theetching of the photoresist layer 128 may result in a hardening of theexposed surface, such that the hardened portion may be more chemicallyresistant than the unexposed portions of the photoresist layer 128. Forexample, the exposed portion (e.g. residual polymer 132) of thephotoresist layer 128 may be more densified than unexposed portions,such that the photoresist layer 128 may be more difficult to removeusing plasma etch processing or wet chemical etch processing. Therefore,it may be desirable to treat the residual polymer 132 to make themeasier to remove. The treatment may include the same or similar UVtreatment steps described below.

At block 114 in FIG. 1B, the substrate 104 may be exposed toultra-violet (UV) light 126 to improve the selectivity of any chemistrythat may be used to remove the residual polymer 132 from the organicpolymer 126 and the photoresist layer 128. The UV light 126 may includeelectromagnetic radiation that has a wavelength of at least 100 nm. Inone embodiment, the UV light 126 may include one or more wavelengths ofelectromagnetic radiation that may be exposed to the substrate at thesame time or in a sequential manner. In one embodiment, a singlewavelength of UV light 126 may be used to the treat the substrate 104.The UV light 126 can make the photoresist layer 128 and residual layer126 more amenable to removal through a variety of mechanisms.

In another embodiment, two different wavelengths of UV light 126 may beused to treat the substrate 104. The first wavelength of light may beless than 200 nm and the second wavelength of light may be greater than200 nm. The UV light 126 may have a dose of up to 150 J/cm2. In anotherembodiment, the first wavelength of UV light 126 may about 185 nm andthe second wavelength of UV light 126 may be about 254 nm.

In another embodiment, the distribution of UV light 126 wavelength mayalso vary during the exposure process in block 114. For example, the UVlight 126 may include at least 10% of the first wavelength with theremainder including UV light 126 of the second wavelength. In onespecific embodiment, at least 10% of the UV light 126 may include awavelength of about 185 nm with the remainder of the UV light 126 havinga wavelength of about 254 nm.

In addition to the UV light 126, the exposure process may also include areactive gas 134 that may weaken the residual layer 132 and the exposedsurface of the photoresist layer 128 and make bother layers moresusceptible to removal (e.g. improved selectivity). The reactive gas mayinclude, but is not limited to, monoatomic oxygen, diatomic oxygen,and/or ozone.

At block 116, the combination of the UV light 126 and the reactive gas134 may oxidize and/or weaken the residual polymer layer 136 and asurface 138 of the photoresist layer 128. The reactive gas 134 mayinclude diatomic oxygen that may be used to generate ozone when thereactive gas 134 is exposed to the UV light 126 or any other energysource. At a minimum, the combination of the UV light 126 and/or thereactive gas 134 may be used to change a surface state of the residualpolymer 136. For example, the residual polymer 136 and/or the weakenedphotoresist layer 138 may be highly absorbent to at least a portion ofthe UV light 126 and induces the excitation of electrons that canfacilitate the breaking of bonds in the weakened residual polymer 136and/or the weakened surfaces 138 of the photoresist layer 128. In oneembodiment, the photoresist layer 128 may be more highly absorbent tothe 185 nm wavelength UV light 126 and may be more likely to break thebonds in the photoresist layer 128. On the other hand, the 254 nm UVlight 126 may not be as absorbent to the underlying layers, but theremay be a much higher fluence of 254 nm photons with enough energy tobreak the bonds in the underlying layers. The higher UV light 126wavelength may be more likely to break the carbon chain in theunderlying layers than the UV light 126 with a lower wavelength.

The reactive gas 134 may also make the weakened residual polymer 136more hydrophilic, such that the weakened residual polymer 136 may bemore easily removed in a subsequent wet chemical process.

At block 118, a wet chemical process may be used to remove thephotoresist layer 128 and the weakened residual polymer 136 to exposethe organic polymer 126. In one embodiment, the wet chemical process mayinclude one or more steps that may include one or more of the followingchemicals: ammonium hydroxide, hydrogen peroxide, water, an aqueous,semi-aqueous, non-aqueous chemical solution, or any combination thereof.Accordingly, the organic polymer 126 may form a pattern on the substrate104 following the removal of the photoresist layer 128 and the residualpolymer 136, 138. In one instance, the pattern may include parallel orsubstantially parallel lines of the organic polymer 126 across thesubstrate 104.

In one embodiment, the wet chemical process may include a combination ofammonium hydroxide, hydrogen peroxide, and water in a ratio of 1:1:5with 27%, by weight, of ammonium hydroxide and 30% of hydrogen peroxide.In one instance, the temperature of that aforementioned combination maybe 50° C. and the substrate 104 may be exposed to the combination for upto two minutes.

In another embodiment, the wet chemical process may include, but is notlimited to, a one or more of the following chemicals:tetramethylammonium, N-Methylpyrrolidone and/or dimethyl sulfoxide. Theaforementioned wet chemical combination may be heated between 45°-65° C.and exposed to the substrate 104 for up to two minutes. In one specificembodiment, the substrate 104 exposure time may be one minute.

At block 120, a neutral copolymer layer 140 may be deposited on thesubstrate 104 and may cover the organic layer 126 and spaces betweenportions of the organic layer 126. In one embodiment, the neutralcopolymer layer may be grafted to the substrate 104 and not the organiclayer 126. The grafting process may include a baking step that less than300° C. Generally, the neutral copolymer layer 140 may not have achemical affinity to the organic layer 126 or subsequent BCP layer (notshown) deposited on the substrate 104. The neutral copolymer layer 140may include, but is not limited to, non-aligned copolymer blocks.

At block 122, non-grafted portions of the neutral copolymer layer 140may be removed from the substrate 104 using a rinse or chemical processthat minimizes the step height difference between the organic layer 126and the neutral copolymer layer 140, as shown in FIG. 1C. The stepheight being the difference in thickness between the substrate 104 andthe opposing surface of the organic layer 126 and the neutral copolymerlayer 140. For example, the surfaces of the organic layer 126 and theneutral copolymer layer 140 that are opposite the substrate 104 may beflush or substantially flush with each other, such that the step heightdifference is minimal.

At block 124, a non-aligned or random copolymer layer 142 may bedeposited over the neutral copolymer layer 140 and the organic polymer126. The random copolymer layer 142 may include at least two polymerblocks that can self-organize or self-assemble in a predictable mannerduring subsequent processing of the substrate 104. For example, thepolymer blocks may be immiscible and may segregate under appropriateconditions to form domains (not shown) predominantly containing a singleblock species or an alternating pattern of each species. The randomcopolymer layer 142 may be deposited by various methods, including, butnot limited to, spin-on coating, spin casting, brush coating, or vapordeposition. For example, the random copolymer layer 142 may be providedas a solution in a carrier solvent such as an organic solvent, e.g.,toluene. The solution may be applied to the substrate 104 and theneutral copolymer layer 140 and the carrier solvent may be subsequentlyremoved to provide the random copolymer layer 142. The random copolymerlayer 142 may include, but is not limited to, two or more species ofpolymers that may include polystyrene and polymethylacrylate (PMMA).

It will be appreciated that the different species are understood toself-aggregate due to thermodynamic considerations in a process similarto the phase separation of materials. The self-organization is guided bythe physical interfaces organic layer 126 and the neutral copolymerlayer 140, as well as the chemical affinities for each other.Accordingly, the constituent blocks of the block copolymers can orientthemselves along the length of the patterned portions of the substrate104. The self-organization may be facilitated and accelerated byannealing the layered structure illustrated adjacent to block 124. Thetemperature of the annealing process may be chosen to be sufficientlylow to prevent adversely affecting the block copolymers or the layeredstructure. The anneal may be performed at a temperature of less thanabout 350° C., less than about 300° C., less than about 250° C., lessthan about 200° C. or about 180° C. in some embodiments. According toanother embodiment, the annealing process may include a solvent anneal,which generally reduces the annealing temperature.

The anneal time may range from about several hours to about 1 minute.For example, annealing times for temperatures above 250° C. may rangefrom about 1 hour to about 2 minutes, from about 30 minutes to about 2minutes, or from about 5 minutes to about 2 minutes.

According to one embodiment, the annealing temperature may be within therange from about 260° C. to about 350° C. wherein the low oxygenatmosphere comprises less than about 40 ppm oxygen. For example, thelayer of the block copolymer 380 may be exposed to annealing conditionsof 310° C. in a low oxygen environment (e.g., no more than 300 ppm) forabout a 2 minutes to about 5 minutes.

The annealing of the random copolymer layer 142 may facilitate theself-assembly of the block copolymer into a plurality of alternatingspecie domains aligned side-by-side as shown in the embodimentsillustrated in FIG. 2.

In other embodiments, the DSA template may be formed using a variety ofprocess flows that are different than the process flow illustrated inFIGS. 1A-1C. The scope of this disclosure may not be limited to theFIGS. 1A-1C flow where the guide stripe (e.g., organic polymer 126) isdeposited and patterned, and the neutral layer (e.g., neutral copolymerlayer 140) is backfilled. In one specific embodiment, the neutral layermay be deposited and patterned with a trench line, and the guidematerial may be back-filled into the trench. In this way, the firstlayer deposited may be neutral in contrast to the PS layer of the FIGS.1A-1C embodiment and the backfill layer may act as the guiding layerinstead of being neutral. The patterning of the neutral layer mayinclude an etch and organic strip that may be similar to the process inFIG. 1A-C. For example, the substrate 104 may be coated with a neutrallayer that may be patterned and etched, and the trench may be backfilledby a Poly(styrene) based brush material, baked and rinsed, just asdepicted in the illustration opposite block 122 in FIG. 1C. Suchprocessing will yield the same chemical template used to direct theself-assembly of the block copolymer (i.e., FIG. 1C, block 122), butwill do so through a different set of processing steps. The residuallayer may be formed on the PS layer during the etch process.Accordingly, the residual layer may be removed using UV processingdescribed above.

FIG. 2 illustrates a 1× frequency embodiment 200 of the block copolymerlayer and a 3× frequency embodiment 202 of the block copolymer layerthat may be implemented, at least in part, by the annealing of therandom copolymer layer 142. However, the frequency of the alternatingspecies may not be limited to 1× and 3× and may include any frequencybetween 1× and 10× or more. The annealing may result in a self-assemblyof alternating species (e.g., polystyrene 206 and PMMA 208) that in aside-by-side manner and opposite the organic layer 126 and the neutralcopolymer layer 140. The domain size (Lo) 210 may be represented by theone iteration of the width of each species that may be adjacent to eachother. The Lo pattern may be repeated across the substrate to form anarray of lines and spaces that may be parallel to each other. Similarly,the underlying organic layer 126 and the neutral copolymer layer 140 mayvary within a period distance 212 in which the two species alternate asshown in FIG. 2. The placement of polystyrene domain 206 and the PMMAdomain 208 may vary with the structure of the underlying layer and mayrepeat at a certain frequency between the organic layer 126 and theneutral copolymer layer 140. FIG. 2 merely includes two representativeembodiments that use different pattern frequencies.

In the 1× frequency embodiment 200, the alternating species maycorrelate with the corresponding underlying layers in a one-to-onemanner, such that the polystyrene blocks 206 may be opposite one of theneutral copolymer layer 140 blocks. The polystyrene blocks 206 and thePMMA blocks 208 may be parallel or substantially parallel to each other.The degree of quality of the formation of the DSA template may bemeasured based on the how parallel the lines and/or space may be over asurface area.

In one embodiment, the parallel lines/spaces may be at least 95%parallel or substantially parallel over a region with a surface area ofat least 1 μm². In one specific embodiment, the surface area may be1.2656 μm². In another embodiment, the quality of the parallellines/spaces may be at least 95% parallel over a surface area that mayinclude an array of at least 40 lines/spaces over a surface area thatmay include more than a majority of the array. For example, the arraysurface area may include the entire array except for the surface areathat may be within 10 Lo of the array edge or perimeter.

In certain instances, the quality of array may be classified into two ormore categories that may segregate the arrays for the purpose of qualitycontrol. For example, the arrays may be binned into three categories95%-100%, 60%-94%, and less than 59%. In one instance, the passingcriteria may be 95%-100% to control or qualify the DSA processingscheme. In another instance, the passing criteria may be 60%-100%, inthat structures that are less than 59% would not pass in eitherembodiment.

In other embodiments, the domain size 210 and the period distance 212may vary from the 1:1 ratio illustrated in the 1× frequency embodiment200. Accordingly, the overlap of different species may be used toselectively etch different patterns into the substrate 104 or underlyinglayers than by using the 1× frequency embodiment 200.

In the 3× frequency embodiment 202, the domain size (Lo) 210 mayalternate at a higher frequency within the period distance 214, suchthat the domain size 210 may alternate several times within the givenperiod distance 214. In this embodiment, the period distance 214 mayextend further than is illustrated in FIG. 2 as represented thecontinuation marker 216. In this instance, the ratio of the overlyingand underlying layers may be 3:1. However, in other embodiments, theratio may be up to 10:1. Additionally, the quality criteria describedabove in the description of the 1× frequency embodiment 200 may also beused to rate and/or classify the lines/spaces in the overlying layer inthe 3× frequency embodiment 202.

FIG. 3 includes an illustration of a flow diagram 300 with correspondingillustrations 302 for a method to selectively remove a first organicfilm an underlying second organic film formed on a substrate 104. Theremoval selectivity may enable a minimal change in thickness or surfacestate of the underlying organic film.

At block 304, a first organic material 312 may be deposited on thesubstrate 104 using any known deposition technique that may include, butis not limited to, chemical vapor deposition or spin-on coating. In oneembodiment, the first organic layer 312 may be any radiation sensitivecomposition that chemically reacts when exposed to visible light, deepultraviolet (DUV) light, extreme ultraviolet (EUV) light, electron beamand X-ray radiant energy are radiation types commonly used today inphotolithography processes. When exposed to radiation, the bonds of themolecules in the photoresist layer 128 may break or become more soluble,such that the exposed portion may be dissolved using a photoresistdeveloper chemical. The photoresist may include, but is not limited to,one or more of the following: protected or unprotected copolymers ofmethacrylic, protected or unprotected acrylic conmonomers, styrene,hyrdoxystyrene, or protected or unprotected hyrdoxystyrene comonomers.

At block 306, a second organic film 314 may be deposited on the firstorganic layer 312, such the two organic films physically interface witheach other and they are relatively distinguishable from each other,despite any similar organic nature of the two films. In one embodiment,the second organic film 314 may be an anti-reflective material thatenables the transmission of light into the second organic film 314, butlimits the amount of light that may be reflected out from the secondorganic layer 314.

At block 308, a first portion of the second organic layer 314 may beremoved using a combination of UV light 126 and oxygen 126. The firstportion may include at least 40% of the thickness of the second organiclayer 314, as illustrated different in thickness between by the thinnersecond organic layer 316 and the second organic layer 312 illustrated inFIG. 3.

In one embodiment, the substrate 104 may be exposed to ultra-violet (UV)light 126 remove the first portion of the second organic layer 314and/or to improve the selectivity of any chemistry that may be used tothe remainder, or second portion, of the second organic layer 314. TheUV light 126 may include electromagnetic radiation that has a wavelengthof at least 100 nm. In one embodiment, the UV light 126 may include oneor more wavelengths of electromagnetic radiation that may be exposed tothe substrate at the same time or in a sequential manner. In oneembodiment, a single wavelength of UV light 126 may be used to the treatthe substrate 104.

In another embodiment, two different wavelengths of UV light 126 may beused to treat the second organic layer 314. The first wavelength oflight may be less than 200 nm and the second wavelength of light may begreater than 200 nm. The UV light 126 may have a dose of up to 150J/cm2. In another embodiment, the first wavelength of UV light 126 mayabout 185 nm and the second wavelength of UV light 126 may be about 254nm.

In another embodiment, the distribution of UV light 126 wavelength mayalso vary during the exposure process in block 308. For example, the UVlight 126 may include at least 10% of the first wavelength with theremainder including UV light 126 of the second wavelength. In onespecific embodiment, at least 10% of the UV light 126 may include awavelength of about 185 nm with the remainder of the UV light 126 havinga wavelength of about 254 nm.

In addition to the UV light 126, the exposure process may also include areactive gas 134 that may weaken the second organic layer 314. Thereactive gas may include, but is not limited to, monoatomic oxygen,diatomic oxygen, and/or ozone.

The combination of the UV light 126 and the reactive gas 134 may oxidizeand/or weaken the second organic layer 314. The reactive gas 134 mayinclude diatomic oxygen that may be used to generate ozone when thereactive gas 134 is exposed to the UV light 126 or any other energysource. At a minimum, the combination of the UV light 126 and/or thereactive gas 134 may be used to change a surface state of the secondorganic layer 314. The reactive gas 134 may also make the weakenedsecond organic layer 314 more hydrophilic, such that the weakened secondorganic layer 316 may be more easily removed in a subsequent wetchemical process.

At block 310, a wet chemical treatment may be used to remove a secondportion of the second organic layer 316 such that any changes to thethickness and/or surface state of the first organic layer 312 may beminimal. The wet chemical treatment may include, but is not limited to,the wet chemical treatments described in the description of block 118.

It is to be appreciated that the Detailed Description section, and notthe Abstract section, is intended to be used to interpret the claims.The Abstract section can set forth one or more, but not all exemplaryembodiments, of the present disclosure, and thus, is not intended tolimit the present disclosure and the appended claims in any way.

While the present disclosure has been illustrated by the description ofone or more embodiments thereof, and while the embodiments have beendescribed in considerable detail, they are not intended to restrict orin any way limit the scope of the appended claims to such detail.Additional advantages and modifications will readily appear to thoseskilled in art. The invention in its broader aspects is therefore notlimited to the specific details, representative apparatus and method andillustrative examples shown and described. Accordingly, departures maybe made from such details without departing from the scope of thegeneral inventive concept.

What is claimed is:
 1. A method for a directed self-assembly techniquefor patterning a substrate, comprising: coating the substrate with apolymer; heating the polymer to a bake temperature to increase a densityof the polymer; patterning the polymer using a layer of photoresist;removing a portion of the polymer that is not covered by photoresist;generating a residual polymer on at least one side sidewall of thepolymer during the removal of the portion of the polymer, oxidizing aportion of the photoresist using oxygen and one or more wavelengths ofultraviolet light (UV); changing the surface state of the residualpolymer using the oxygen and the one or more wavelengths of ultravioletlight; and removing the photoresist and the residual polymer to exposethe polymer.
 2. The method of claim 1, further comprising: coating thepatterned polymer and the substrate with a selective material thatadheres more strongly to the substrate than the patterned polymer; andremoving the selective material that is above the exposed polymer. 3.The method of claim 2, wherein the selective material comprises a randomcopolymer layer that can form a block copolymer when the randomcopolymer layer is annealed.
 4. The method of claim 3, wherein thepositive tone photoresist or the negative tone photoresist comprise oneor more of the following: protected or unprotected copolymers ofmethacrylic; protected or unprotected acrylic conmonomers; styrene;hyrdoxystyrene; or protected or unprotected hyrdoxystyrene comonomers.5. The method of claim 1, wherein the wavelength comprises a wavelengththat is less than 200 nm or a wavelength that is greater than 200 nm. 6.The method of claim 5, wherein the ultraviolet light comprises a lowerwavelength dose between 0.01 J/cm2 to 150 J/cm2 for the wavelength thatis greater than 200 nm or a higher wavelength dose between 0.01 J/cm2 to13 J/cm2 for the wavelength that is less than 200 nm.
 7. The method ofclaim 1, wherein the polymer comprises polystyrene.
 8. The method ofclaim 1, wherein the one or more wavelengths of UV light comprises afirst wavelength that is less than 200 nm and a second wavelength of UVlight comprises a wavelength that is greater than 200 nm.
 9. The methodof claim 1, wherein the ultraviolet light comprises at least 10% oflight that has a wavelength that is less than 200 nm.
 10. The method ofclaim 1, wherein the baking temperature comprises a temperature between200 C and 310 C.
 11. A method for removing photoresist from a substrate,comprising: patterning the photoresist on the substrate comprising apolymer; removing the polymer that is exposed by the patternedphotoresist, the removal generating a residual polymer on sidewalls ofthe polymer and hardening the photoresist; exposing the substrate toultraviolet light and oxygen, the ultraviolet light comprising one ormore wavelengths of UV light; and removing the photoresist and theresidual polymer using a wet chemical process to form a patternedpolymer on the substrate.
 12. The method of claim 11, wherein thepolymer comprises polystyrene.
 13. The method of claim 11, wherein theexposure of ultraviolet light oxidizes the hardened photoresist andresidual polymer.
 14. The method of claim 11, wherein the wet chemicalprocess comprises ammonium hydroxide, hydrogen peroxide, water, anaqueous, semi-aqueous or non-aqueous chemical solution.
 15. The methodof claim 11, wherein the wavelength comprises a wavelength no more than185 nm.
 16. The method of claim 15, wherein the wavelength comprises awavelength of at least 220 nm.
 17. The method of claim 11, wherein thewavelengths comprises a first wavelength that is less than 200 nm and asecond wavelength that is greater than 200 nm.
 18. The method of claim17, wherein the wavelength that is greater than 200 nm comprises awavelength of about 254 nm.
 19. The method of claim 11, wherein thepolymer comprises a thickness between 5 nm and 20 nm.
 20. The method ofclaim 11, wherein the polymer comprises a sidewall angle between 40degrees and 105 degrees from a bottom surface of the polymer.
 21. Amethod for removing first organic layer from a substrate, comprising:depositing the first organic layer on the substrate comprising a secondorganic layer; removing a first portion of the first organic layer byexposing the first organic to ultraviolet light and oxygen; and removinga second portion of the first organic layer using a wet chemicalprocess.
 22. The method of claim 21, wherein the first portion comprisesat least 40% of a thickness of the first organic layer and the secondportion comprises a remainder of the thickness of the first organiclayer.
 23. The method of claim 21, wherein the first organic layercomprises a photoresist, and the second organic layer comprises anorganic anti-reflective material, and the substrate comprises silicon.24. The method of claim 21, wherein, following the removal of the firstportion, the first organic layer comprises a higher oxygen concentrationthan the second organic layer.
 25. The method of claim 21, wherein theultraviolet light comprises a first distribution of wavelengths lessthan 200 nm and a second distribution of wavelengths greater than 200 nm26. The method of claim 25, wherein the wavelength that is less than 200nm comprises a wavelength no more than 185 nm.
 27. The method of claim26, wherein the wavelength that is greater than 200 nm comprises awavelength of at least 220 nm.
 28. The method of claim 21, wherein theultraviolet light comprises a wavelength of about 185 nm.
 29. The methodof claim 28, wherein the wavelength that is greater than 200 nmcomprises a wavelength of about 254 nm.
 30. The method of claim 21,wherein the ultraviolet light comprises a wavelength greater than 100nm.